1. Field of the Invention
The present invention relates to a clock signal detection circuit that detects whether or not a clock signal is supplied thereto and further to a semiconductor integrated circuit using such a clock signal detection circuit,
2. Description of the Related Art
Semiconductor integrated circuits for handling digital signals commonly contain many circuits that operates in sync with a clock signal, such as a flip-flop circuit. In order to detect whether or not the clock signal is supplied to such a circuit, clock detection circuits are sometimes used in such semiconductor integrated circuits,
Conventional clock signal detection circuits sample a target clock signal based on a reference clock signal to detect whether or not a level of the target clock signal changes, However, this is problematic in that a large-scale circuit is necessary to perform such detection causing large power consumption, Moreover, the reliability of detection is not very high,
Incidentally, in Japanese unexamined patent publication No, 10-123996 (Pages 1 and 5, FIG. 1), a bolometer-type infrared ray sensor is described as an example of a semiconductor device equipped with a pixel protection circuit. This bolometer-type infrared ray sensor consistently watches a plurality of data signals and clock signals input thereto by respective monitoring circuit, thus preventing the pixel from being selected by turning off a switch if a scanning circuit stops or operates improperly because of, for example, disconnection of these signals,
In the bolometer-type infrared ray sensor, a horizontal clock monitoring circuit comprises a retriggerable monostable multivibrator. The horizontal clock monitoring circuit outputs a signal for enabling a horizontal switch to select pixels if a horizontal clock signal is continuously input, but if the horizontal clock stops, the horizontal clock monitoring circuit outputs a signal for making the horizontal switch move to a shut-down state after a time constant determined by a capacitor and a resistor has elapsed, thus protecting the device by preventing pixels from being deteriorated in quality or broken,
Here, the time constant determined by the capacitor and resistor is selected to a time duration throughout which any specific one of the pixels can be continuously selected without any deterioration in quality or breaking-down of the pixel caused by self-heating of a bolometer. However, monostable multivibrators have a large circuit scale and accordingly require large power consumption, Furthermore, if a capacitor is formed inside a semiconductor integrated circuit, a particularly large area is necessary among passive elements because the capacitor has a structure of two parallel electrodes holding a dielectric material therebetween.
Consequently, taking the above into consideration, the present invention advantageously provides a clock signal detection circuit and a semiconductor integrated circuit using the same clock signal detection circuit that is able to reliably detect whether or not a clock signal is supplied thereto with a reduced circuit scale and reduced power consumption.